B2 W2 - Pathophysiology and Clinical Aspects of Asthma (LT) Flashcards
What is the estimated prevalence of asthma in the UK?
10-15% of the population.
What is the hygiene hypothesis?
This theory suggests that extreme cleanliness in childhood increases the likelihood of developing asthma.
Name two environmental factors, aside from hygiene, that contribute to asthma development.
Pollution and occupational sensitizers.
What are the two main classifications of asthma?
-
Extrinsic (“atopic”) asthma
and - Intrinsic asthma.
What is the typical onset age for extrinsic asthma?
Childhood.
What is the typical onset age for intrinsic asthma?
Middle age.
What are the three key features of asthma pathophysiology?
- Reversible airway obstruction
- Airway hyper-responsiveness
- Airway inflammation.
List four key features visible in a histological cross-section of a bronchiole from a patient with severe asthma.
- Mucus plugging
- Inflammatory cells infliltration (especially mast cells, eosinophils, and macrophages)
- Hypertrophy (and hyperplasia) of smooth muscle
- An increased number of goblet cells in the epithelium.
Which cell releases histamine in a process known as ‘degranulation’?
Mast cells.
Which antibody class is responsible for binding allergens and causing degranulation of mast cells?
IgE.
Which T lymphocyte type is most important in the response to allergens in asthma?
- T-helper cells type 2 (Tн2).
- A subtype specifically implicated in allergic responses
What happens during the immediate/early phase of asthma pathogenesis?
The allergen is recognised and bound by IgE antibodies, which then bind to and activate mast cells and cause them to degranulate.
What is the timeframe for the immediate/early phase of asthma pathogenesis?
0-60 minutes after allergen exposure.
What happens during the late phase of asthma pathogenesis?
Chemical mediators (released by the mast cells and TH2 cells) cause
- vascular leakage and oedema
- Infiltration of eosinophils and neutrophils
- Mucus secretion.
What is the timeframe for the late phase of asthma pathogenesis?
1-8 hours after allergen exposure.
What happens during the chronic remodelling phase of asthma pathogenesis?
Structural changes in the airways, often referred to as airway remodelling inluding:
- Smooth muscle hypertrophy and hyperplasia
- Epithelial damage
- Basement membrane thickening.
What is the timeframe for the chronic remodelling phase of asthma pathogenesis?
Months to years after the initial allergen exposure.
List four classic symptoms of asthma.
- Cough
- Wheeze
- Chest tightness
- Dyspnoea (Shortness of breath)
Why is asthma difficult to diagnose in young children?
Diagnostic tests like peak flow or spirometry testing are difficult to perform on young children.
List four signs of asthma exacerbation a doctor may find on examination.
- Difficulty completing full sentences
- High respiratory rate (tachypnoea)
- High heart rate (tachycardia)
- Wheeze
Why might reduced breath sounds indicate a more severe asthma exacerbation?
They suggest very little air is moving in and out of the lungs, possibly due to airway blockage by mucus.
Apart from patient history and response to treatment, list some investigations that can be used to help diagnose asthma.
- Reversibility on spirometry
- Diurnal variation on peak flow monitoring
- Fractional exhaled nitric oxide (FeNO)
- Blood eosinophils.
What is Fractional Exhaled Nitric Oxide (FeNO)
- FeNO measurement is a relatively newer non-invasive test that measures the level of nitric oxide in exhaled breath.
- Elevated FeNO levels can indicate airway inflammation, a characteristic feature of asthma.
- This test is particularly useful in identifying eosinophilic airway inflammation, a specific type of inflammation often present in asthma.
What key feature on peak flow monitoring would suggest a diagnosis of asthma?
Diurnal variation.
Why would blood eosinophils be used in the diagnosis of asthma?
Elevated blood eosinophil counts can suggest an underlying allergic or inflammatory process, supporting an asthma diagnosis.
What is the benefit of using a patient’s normal average peak flow for monitoring?
It allows for comparison with measurements taken when they are unwell.
What is the first treatment usually given for an acute asthma attack?
β2-agonist bronchodilators (e.g., salbutamol).
What other treatment should all asthma attacks be treated with?
Corticosteroids.
What is the minimum recommended duration for corticosteroid treatment in acute asthma?
5 days.
Aside from oxygen, β2-agonist bronchodilators, and corticosteroids, list some other treatments that may be used in acute asthma management.
- Ipratropium bromide
- Magnesium sulphate (IV)
- Aminophylline (IV)
- Prednisolone
- Hydrocortisone
- Antibiotics
What is the main aim of chronic asthma management?
To prevent acute exacerbations and reduce inflammatory changes that lead to airway remodelling.
What is the recommended first-line treatment for most patients with asthma?
Inhaled corticosteroids (ICS).
Name two categories of asthma inhalers and give an example of each.
- Relievers (e.g., salbutamol)
- Controllers (e.g., salmeterol).
Why is proper inhaler technique important?
It ensures the patient receives the full benefit of the medication and reduces the risk of side effects from swallowing it.
Just think about the house scene
How does the stepwise approach to managing chronic asthma work?
- The approach involves assessing asthma symptoms and adjusting treatment accordingly.
- If symptoms worsen, treatment is stepped up by adding or increasing medication.
- Conversely, if symptoms remain well controlled, treatment can be stepped down to reduce the risk of side effects.
What is the typical pattern of diurnal variation in asthma?
- Asthma typically improves during the day and worsens overnight.
- This is due to fluctuations in cortisol levels, which are naturally higher in the morning and lower at night.
Why is diurnal variation important in asthma?
- It is a key feature that can help diagnose asthma and assess its severity.
- This variation is reflected in peak flow measurements, which tend to be higher in the evening and lower in the morning for asthmatics.
What are the consequences of poor inhaler technique?
- Poor inhaler technique can lead to the medication being deposited in the mouth and throat instead of the lungs.
- This reduces the effectiveness of the treatment and increases the risk of side effects, such as oral thrush from inhaled corticosteroids.
What is ‘mucus plugging’ in asthma?
- Mucus plugging refers to the blockage of airways by thick mucus, a common occurrence during severe asthma exacerbations.
- It can significantly hinder airflow and worsen breathing difficulties.
Why is a ‘silent chest’ a concerning sign in an acute asthma attack?
- A silent chest, where wheezing is no longer audible, indicates severely restricted airflow and is a sign of life-threatening asthma.
- This situation requires immediate medical attention.
What role do antibiotics play in asthma management?
- Antibiotics are not routinely used in asthma management.
- They are only prescribed if there is evidence of a bacterial infection contributing to the asthma exacerbation, such as pneumonia.
Why is it important to manage chronic asthma effectively?
- Effective management aims to prevent acute exacerbations, as frequent asthma attacks can lead to a decline in lung function and increase the risk of future severe attacks.
- It also helps reduce the inflammatory changes that can cause irreversible airway remodelling.
What are some examples of occupational sensitizers that can contribute to asthma?
- Glues
- Insulation material
- Wood dust
- Latex
- Rat urine
Why is it thought that children growing up on farms are less likely to develop asthma?
This observation is linked to the hygiene hypothesis, which suggests that exposure to a wider range of microbes in a farm environment might help to train the immune system and reduce the risk of developing allergies and asthma.
What does the early phase of an asthma attack involve?
- The early phase of an asthma attack, which occurs within the first hour after allergen exposure, involves the binding of allergens to IgE antibodies.
- These activated IgE antibodies then bind to mast cells, leading to mast cell degranulation.
What is the late phase of an asthma attack charecterised by?
- The late phase, which happens 1-8 hours after allergen exposure, is characterized by vascular leakage and oedema.
- This is due to the chemical mediators released by mast cells and T helper 2 (TH2) cells.
Repetitive exposure to allergens or triggers can cause what in the asthmatic airway?
- Chronic changes
These changes, part of the chronic remodelling phase, include:
- hypertrophy of smooth muscle
- hyperplasia of smooth muscle and epithelial cells.
How can asthma symptoms can present differently in younger individuals compared to older individuals?
- In younger individuals, particularly those with atopic asthma, asthma symptoms often coincide with other inflammatory or allergic symptoms such as hayfever or eczema.
- This suggests a potential link between asthma and these conditions in this age group.
What clinical sign could indicate a more severe asthma exacerbation?
- Reduced breath sounds during an asthma exacerbation are a worrying sign.
- This suggests a more severe attack because it might indicate that very little air is entering or exiting the lungs.
- This could be due to mucus plugging, where mucus blocks the airways.
Usually, what colour are reliever inhalers?
Blue
Usually, what colour are ‘controller’ inhalers?
Green
Usually, what colour are ‘preventer’ inhalers?
Brown/ Orange
Usually, what colour are ‘combination’ inhalers?
Purple
When is asthma considered ‘Life-threatening’?
Anyoneof the following, in a patient with severe asthma:
Clinical signs:
- Altered conscious level
- Exhaustion
- Arrhythmia
- Hypotension
- Cyanosis
- Silent chest
- Poor respiratory effort
or
Measurements:
- Peak flow <33% best or predicted
- Oxygen saturations <92%
- PaO2 <8 kPa
- ‘Normal’ PaCO2 (4.6 - 6.0 kPa)
When is an acute asthma attack considered severe?
Any one of:
- Peak flow 33-50% best (or predicted)
- Respiratory rate ≥25/min
- Heart rate≥110/min
- Inability to complete sentences in one breath
